The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Takeshi Endo - One of the best experts on this subject based on the ideXlab platform.
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Special Issue "Ring-Opening Polymerization".
Molecules (Basel Switzerland), 2016Co-Authors: Takeshi Endo, Atsushi SudoAbstract:Ring-Opening Polymerization (ROP) has gained much attention because of its usefulness to synthesize polymers with main chains inheriting the heteroatoms and functional groups from the corresponding monomers.[...]
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Radical Ring‐Opening Polymerization and coPolymerization with expansion in volume
Journal of Polymer Science: Polymer Symposia, 2007Co-Authors: William J. Bailey, Takeshi EndoAbstract:Although Ring-Opening Polymerization involving ionic intermediates and Ziegler catalysts are quite extensively used in polymer chemistry, free radical Ring-Opening Polymerization is extremely rare. We have been able to show that unsaturated spiro ortho carbonates will undergo double Ring-Opening Polymerization under radical conditions. In addition these monomers will undergo ready coPolymerization with common monomers, such as styrene, methyl methacrylate, and diallyl carbonate. Since this process involves a double Ring-Opening, a slight expansion in volume occurs. For a number of industrial applications, such as precision castings, strain-free composites, binders for solid propellants, high strength adhesives, dental fillings, and rock-cracking materials, it is highly desirable to have monomers that expand on Polymerization. In the formation of composites, such a monomer might minimize poor adhesion between the matrix and the reinforcing agent or eliminate microcracks. Formation of additional polymers usually involves shrinkage since the monomer undergoes a transition from a van der Waals distance to a covalent distance in the polymeric material. Ring-Opening Polymerization usually involves somewhat less shrinkage because for every new bond that is formed involving a shift from a van der Waals distance to a covalent distance, another bond is broken involving a shift from a covalent distance to a near van der Waals distance. Thus, if monomers are utilized in which two bonds are broken for every new bond that is formed in the Polymerization process, near zero shrinkage or expansion takes place.
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Living Ring‐Opening Polymerization of cyclic thiocarbonate
Macromolecular Symposia, 2003Co-Authors: Takeshi Endo, Nobukatsu Nemoto, Fumio SandaAbstract:This work deals with the cationic Ring-Opening Polymerization of a cyclic thiocarbonate, 5,5-dimethyl-1,3-dioxane-2-thione (1). The Polymerization was carried out with 2 mol% of trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, boron trifluoride etherate, or triethyloxonium tetrafluoroborate as an initiator to afford the polythiocarbonate with the narrow molecular weight distribution (M n = 11200-31000, M w /M n = 1.04-1.15). The molecular weight of the obtained polymer could be controlled by the feed ratio of the monomer to the initiator and increased when the second monomer was added to the Polymerization mixture after quantitative consumption of 1 in the first stage, supporting that the cationic Ring-Opening Polymerization of 1 proceeded via a living process.
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Living Ring-Opening Polymerization of cyclic thiocarbonate
Macromolecular Symposia, 2003Co-Authors: Takeshi Endo, Nobukatsu Nemoto, Fumio SandaAbstract:This work deals with the cationic Ring-Opening Polymerization of a cyclic thiocarbonate, 5,5-dimethyl-1,3-dioxane-2-thione (1). The Polymerization was carried out with 2 mol% of trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, boron trifluoride etherate, or triethyloxonium tetrafluoroborate as an initiator to afford the polythiocarbonate with the narrow molecular weight distribution (M n = 11200-31000, M w /M n = 1.04-1.15). The molecular weight of the obtained polymer could be controlled by the feed ratio of the monomer to the initiator and increased when the second monomer was added to the Polymerization mixture after quantitative consumption of 1 in the first stage, supporting that the cationic Ring-Opening Polymerization of 1 proceeded via a living process.
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Controlled cationic Ring‐Opening Polymerization of cyclic thiocarbonates with ester groups
Journal of Polymer Science Part A: Polymer Chemistry, 2002Co-Authors: Nobukatsu Nemoto, Hisamitsu Kameshima, Fumio Sanda, Kouichi Yoshii, Takeshi EndoAbstract:This work deals with the cationic Ring-Opening Polymerization of the cyclic thiocarbonates 5-benzoyloxymethyl-5-methyl-1,3-dioxane-2-thione (1), 5,5-dimethyl-1,3-dioxane-2-thione (2), and 4-benzoyloxymethyl-1,3-dioxane-2-thione (3). The Polymerization was carried out with 2 mol % trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, boron trifluoride etherate, or triethyloxonium tetrafluoroborate as the initiator to afford the polythiocarbonate with a narrow molecular weight distribution accompanying isomerization of the thiocarbonate group. The molecular weight of the obtained polymer could be controlled by the feed ratio of the monomer to the initiator and increased when the second monomer was added to the Polymerization mixture after the quantitative consumption of the monomer in the first stage. The block coPolymerization of 2 and 3 was also achieved, and this supported the idea that the cationic Ring-Opening Polymerization of these monomers proceeded via a living process. The order of the Polymerization rate was 3 > 2 > 1. The cationic Ring-Opening Polymerization of 1 and 3 involved the neighboRing group participation of ester groups according to the Polymerization rate and molecular orbital calculations with the ab initio method. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 185–195, 2003
Yan Yang - One of the best experts on this subject based on the ideXlab platform.
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lipase esterase catalyzed Ring Opening Polymerization a green polyester synthesis technique
Process Biochemistry, 2011Co-Authors: Yan Yang, Yuanxin Zhang, Chengbai Liu, Wei ShiAbstract:In the last decade, there has been increased interest in lipase/esterase-catalyzed Ring-Opening Polymerization as an alternative to metal-based catalytic processes. This review focuses on three components in the reaction system, namely biocatalysts, reaction medium and monomers. Novel lipases or esterases are described with particular emphasis on, those derived from thermophiles, immobilized enzymes and recombinant whole-cell biocatalysts. Green solvents in enzymatic Ring-Opening Polymerization, including water, ionic liquids, supercritical carbon dioxide and hydrofluorocarbon solvents, are also discussed. Enzymatic Ring-Opening Polymerization is reviewed with regard to the variety of polymers obtainable, such as polyesters, polycarbonates, polyphosphates and polythioesters. Among these, enzymatic synthesis of polyesters has been most widely investigated, and is discussed for lactones with small to large Ring sizes. Finally, the mechanism of enzymatic Ring-Opening Polymerization is described, which is generally accepted as a monomer-activated mechanism. Overall, the review demonstrates that lipase/esterase-catalyzed synthesis of polymers via Ring-Opening Polymerization provides an effective platform for conducting "green polymer chemistry". (C) 2011 Elsevier Ltd. All rights reserved.
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Lipase/esterase-catalyzed Ring-Opening Polymerization: A green polyester synthesis technique
Process Biochemistry, 2011Co-Authors: Yan Yang, Yuanxin Zhang, Chengbai Liu, Wei ShiAbstract:In the last decade, there has been increased interest in lipase/esterase-catalyzed Ring-Opening Polymerization as an alternative to metal-based catalytic processes. This review focuses on three components in the reaction system, namely biocatalysts, reaction medium and monomers. Novel lipases or esterases are described with particular emphasis on, those derived from thermophiles, immobilized enzymes and recombinant whole-cell biocatalysts. Green solvents in enzymatic Ring-Opening Polymerization, including water, ionic liquids, supercritical carbon dioxide and hydrofluorocarbon solvents, are also discussed. Enzymatic Ring-Opening Polymerization is reviewed with regard to the variety of polymers obtainable, such as polyesters, polycarbonates, polyphosphates and polythioesters. Among these, enzymatic synthesis of polyesters has been most widely investigated, and is discussed for lactones with small to large Ring sizes. Finally, the mechanism of enzymatic Ring-Opening Polymerization is described, which is generally accepted as a monomer-activated mechanism. Overall, the review demonstrates that lipase/esterase-catalyzed synthesis of polymers via Ring-Opening Polymerization provides an effective platform for conducting "green polymer chemistry". (C) 2011 Elsevier Ltd. All rights reserved.
Wei Shi - One of the best experts on this subject based on the ideXlab platform.
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lipase esterase catalyzed Ring Opening Polymerization a green polyester synthesis technique
Process Biochemistry, 2011Co-Authors: Yan Yang, Yuanxin Zhang, Chengbai Liu, Wei ShiAbstract:In the last decade, there has been increased interest in lipase/esterase-catalyzed Ring-Opening Polymerization as an alternative to metal-based catalytic processes. This review focuses on three components in the reaction system, namely biocatalysts, reaction medium and monomers. Novel lipases or esterases are described with particular emphasis on, those derived from thermophiles, immobilized enzymes and recombinant whole-cell biocatalysts. Green solvents in enzymatic Ring-Opening Polymerization, including water, ionic liquids, supercritical carbon dioxide and hydrofluorocarbon solvents, are also discussed. Enzymatic Ring-Opening Polymerization is reviewed with regard to the variety of polymers obtainable, such as polyesters, polycarbonates, polyphosphates and polythioesters. Among these, enzymatic synthesis of polyesters has been most widely investigated, and is discussed for lactones with small to large Ring sizes. Finally, the mechanism of enzymatic Ring-Opening Polymerization is described, which is generally accepted as a monomer-activated mechanism. Overall, the review demonstrates that lipase/esterase-catalyzed synthesis of polymers via Ring-Opening Polymerization provides an effective platform for conducting "green polymer chemistry". (C) 2011 Elsevier Ltd. All rights reserved.
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Lipase/esterase-catalyzed Ring-Opening Polymerization: A green polyester synthesis technique
Process Biochemistry, 2011Co-Authors: Yan Yang, Yuanxin Zhang, Chengbai Liu, Wei ShiAbstract:In the last decade, there has been increased interest in lipase/esterase-catalyzed Ring-Opening Polymerization as an alternative to metal-based catalytic processes. This review focuses on three components in the reaction system, namely biocatalysts, reaction medium and monomers. Novel lipases or esterases are described with particular emphasis on, those derived from thermophiles, immobilized enzymes and recombinant whole-cell biocatalysts. Green solvents in enzymatic Ring-Opening Polymerization, including water, ionic liquids, supercritical carbon dioxide and hydrofluorocarbon solvents, are also discussed. Enzymatic Ring-Opening Polymerization is reviewed with regard to the variety of polymers obtainable, such as polyesters, polycarbonates, polyphosphates and polythioesters. Among these, enzymatic synthesis of polyesters has been most widely investigated, and is discussed for lactones with small to large Ring sizes. Finally, the mechanism of enzymatic Ring-Opening Polymerization is described, which is generally accepted as a monomer-activated mechanism. Overall, the review demonstrates that lipase/esterase-catalyzed synthesis of polymers via Ring-Opening Polymerization provides an effective platform for conducting "green polymer chemistry". (C) 2011 Elsevier Ltd. All rights reserved.
Fumio Sanda - One of the best experts on this subject based on the ideXlab platform.
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Living Ring‐Opening Polymerization of cyclic thiocarbonate
Macromolecular Symposia, 2003Co-Authors: Takeshi Endo, Nobukatsu Nemoto, Fumio SandaAbstract:This work deals with the cationic Ring-Opening Polymerization of a cyclic thiocarbonate, 5,5-dimethyl-1,3-dioxane-2-thione (1). The Polymerization was carried out with 2 mol% of trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, boron trifluoride etherate, or triethyloxonium tetrafluoroborate as an initiator to afford the polythiocarbonate with the narrow molecular weight distribution (M n = 11200-31000, M w /M n = 1.04-1.15). The molecular weight of the obtained polymer could be controlled by the feed ratio of the monomer to the initiator and increased when the second monomer was added to the Polymerization mixture after quantitative consumption of 1 in the first stage, supporting that the cationic Ring-Opening Polymerization of 1 proceeded via a living process.
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Living Ring-Opening Polymerization of cyclic thiocarbonate
Macromolecular Symposia, 2003Co-Authors: Takeshi Endo, Nobukatsu Nemoto, Fumio SandaAbstract:This work deals with the cationic Ring-Opening Polymerization of a cyclic thiocarbonate, 5,5-dimethyl-1,3-dioxane-2-thione (1). The Polymerization was carried out with 2 mol% of trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, boron trifluoride etherate, or triethyloxonium tetrafluoroborate as an initiator to afford the polythiocarbonate with the narrow molecular weight distribution (M n = 11200-31000, M w /M n = 1.04-1.15). The molecular weight of the obtained polymer could be controlled by the feed ratio of the monomer to the initiator and increased when the second monomer was added to the Polymerization mixture after quantitative consumption of 1 in the first stage, supporting that the cationic Ring-Opening Polymerization of 1 proceeded via a living process.
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Controlled cationic Ring‐Opening Polymerization of cyclic thiocarbonates with ester groups
Journal of Polymer Science Part A: Polymer Chemistry, 2002Co-Authors: Nobukatsu Nemoto, Hisamitsu Kameshima, Fumio Sanda, Kouichi Yoshii, Takeshi EndoAbstract:This work deals with the cationic Ring-Opening Polymerization of the cyclic thiocarbonates 5-benzoyloxymethyl-5-methyl-1,3-dioxane-2-thione (1), 5,5-dimethyl-1,3-dioxane-2-thione (2), and 4-benzoyloxymethyl-1,3-dioxane-2-thione (3). The Polymerization was carried out with 2 mol % trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, boron trifluoride etherate, or triethyloxonium tetrafluoroborate as the initiator to afford the polythiocarbonate with a narrow molecular weight distribution accompanying isomerization of the thiocarbonate group. The molecular weight of the obtained polymer could be controlled by the feed ratio of the monomer to the initiator and increased when the second monomer was added to the Polymerization mixture after the quantitative consumption of the monomer in the first stage. The block coPolymerization of 2 and 3 was also achieved, and this supported the idea that the cationic Ring-Opening Polymerization of these monomers proceeded via a living process. The order of the Polymerization rate was 3 > 2 > 1. The cationic Ring-Opening Polymerization of 1 and 3 involved the neighboRing group participation of ester groups according to the Polymerization rate and molecular orbital calculations with the ab initio method. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 185–195, 2003
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Radical Ring-Opening Polymerization
Journal of Polymer Science Part A: Polymer Chemistry, 2000Co-Authors: Fumio Sanda, Takeshi EndoAbstract:This chapter deals with radical Ring-Opening Polymerization (radical ROP), which provides us with a strategy for synthesizing heteroatom-containing polymers by radical processes. Various cyclic monomers capable of radically induced ROP are introduced so that the essential items of molecular designs and Polymerization mechanisms can be understood. Recent examples of controlled radical ROPs for well-defined polymer synthesis are also described.
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Cationic Ring-Opening Polymerization behavior of six-membered cyclic sulfite
Macromolecules, 1995Co-Authors: Natsuhiro Azuma, Fumio Sanda, Toshikazu Takata, Takeshi EndoAbstract:Cationic Ring-Opening Polymerization behavior of six-membered cyclic sulfite (1) was examined. 1 was prepared by the reaction of 1,3-propanediol with SOCl 2 in 80% yield. Cationic Ring-Opening Polymerization of 1 was carried out in the presence of cationic initiators such as benzyl bromide (BnBr), BF 3 .OEt 2 , trifluoromethanesulfonic acid (TfOH), and methyl trifluoromethanesulfonate (TfOMe) in bulk to afford a polymer consisting of sulfite and ether moieties. The content of the poly(ether) unit was estimated to be 30-90%. The relative rate of Polymerization by the initiators was estimated to be TfOH :TfOMe :BF 3 .OEt 2 = 3.5 :2.5 :1.0. Judging from the time-conversion curves and time-poly(ether) production curves, the elimination of sulfur dioxide in the propagating end of the polymer was confirmed to depend on the character of the counteranion.
Chengbai Liu - One of the best experts on this subject based on the ideXlab platform.
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lipase esterase catalyzed Ring Opening Polymerization a green polyester synthesis technique
Process Biochemistry, 2011Co-Authors: Yan Yang, Yuanxin Zhang, Chengbai Liu, Wei ShiAbstract:In the last decade, there has been increased interest in lipase/esterase-catalyzed Ring-Opening Polymerization as an alternative to metal-based catalytic processes. This review focuses on three components in the reaction system, namely biocatalysts, reaction medium and monomers. Novel lipases or esterases are described with particular emphasis on, those derived from thermophiles, immobilized enzymes and recombinant whole-cell biocatalysts. Green solvents in enzymatic Ring-Opening Polymerization, including water, ionic liquids, supercritical carbon dioxide and hydrofluorocarbon solvents, are also discussed. Enzymatic Ring-Opening Polymerization is reviewed with regard to the variety of polymers obtainable, such as polyesters, polycarbonates, polyphosphates and polythioesters. Among these, enzymatic synthesis of polyesters has been most widely investigated, and is discussed for lactones with small to large Ring sizes. Finally, the mechanism of enzymatic Ring-Opening Polymerization is described, which is generally accepted as a monomer-activated mechanism. Overall, the review demonstrates that lipase/esterase-catalyzed synthesis of polymers via Ring-Opening Polymerization provides an effective platform for conducting "green polymer chemistry". (C) 2011 Elsevier Ltd. All rights reserved.
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Lipase/esterase-catalyzed Ring-Opening Polymerization: A green polyester synthesis technique
Process Biochemistry, 2011Co-Authors: Yan Yang, Yuanxin Zhang, Chengbai Liu, Wei ShiAbstract:In the last decade, there has been increased interest in lipase/esterase-catalyzed Ring-Opening Polymerization as an alternative to metal-based catalytic processes. This review focuses on three components in the reaction system, namely biocatalysts, reaction medium and monomers. Novel lipases or esterases are described with particular emphasis on, those derived from thermophiles, immobilized enzymes and recombinant whole-cell biocatalysts. Green solvents in enzymatic Ring-Opening Polymerization, including water, ionic liquids, supercritical carbon dioxide and hydrofluorocarbon solvents, are also discussed. Enzymatic Ring-Opening Polymerization is reviewed with regard to the variety of polymers obtainable, such as polyesters, polycarbonates, polyphosphates and polythioesters. Among these, enzymatic synthesis of polyesters has been most widely investigated, and is discussed for lactones with small to large Ring sizes. Finally, the mechanism of enzymatic Ring-Opening Polymerization is described, which is generally accepted as a monomer-activated mechanism. Overall, the review demonstrates that lipase/esterase-catalyzed synthesis of polymers via Ring-Opening Polymerization provides an effective platform for conducting "green polymer chemistry". (C) 2011 Elsevier Ltd. All rights reserved.
